This application claims priority of German application number 199 16 68.4, filed Apr. 14, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an arrangement for transporting cardboard blanks or the like in the flat, in particular for book cover or letter file machines, comprising at least two sequenced transport belts extending parallel to one another which are guided over deflecting wheels, at which transport belts grippers for holding the blanks are applied.
An arrangement of this type is prior art in the Hoerauf brochure BDM 30. The embodiment of the grippers is not described in any detail in this brochure, but the relevant machine in practice is so designed that the blanks were clamped between clamping parts, which engaged with two opposite edges of the blank.
It is an object of the present invention to improve an arrangement of the above mentioned type with regard to the grippers.
This object has been achieved in accordance with the present invention in that the grippers comprise controlled, swivelling clamping elements, which can be opened at the deflecting wheels.
Grippers of this design are capable of holding a blank reliably and with exact positioning. Furthermore, they can grip a blank at a deflecting wheel and let go in time at the other deflecting wheel. This does not involve a complicated process.
Advantageously the grippers are clamped by fixing elements in the teeth gaps of the transport belts, which are toothed belts. By using this type of fixing elements, the grippers can not only be applied easily to the transport belts, they are also adjustable or exchangeable as required.
For the purpose of the invention, the grippers comprise a supporting body on which the respective clamping element is supported with a swivel axle. In this way the grippers are divided into a holding element and a function element.
In an embodiment of the present invention, the clamping elements take the form of essentially L-shaped fingers, whose free limbs can be advanced to the blank in their axial direction. This embodiment requires the smallest possible clamping surface on the blank. With clamping elements of this design, the procedural steps to be carried out by the machine, for example the folding in of an edge by rotating brushes in book cover machines, are not hindered.
Advantageously, the clamping elements are arranged at the front edge in transport direction of the blanks. Thus the blanks are merely drawn along and therefore reliably transported. The other edges of the blank are free so that procedural steps can be carried out there unhindered.
It is provided in preferred embodiments that, at a distance corresponding to the space between two grippers in the transport direction of the transport belts, the deflecting wheels, in the form of toothed belt wheels, each have a milled tooth. Thus, for example, one single tooth gap arises in the circumference of the deflecting wheel, in which gap the affixing structure can engage when the gap passes during rotation. Thus the affixing structure are not hindered by the design type of the deflecting wheel.
In certain preferred embodiments of the present invention, cam discs are provided for controlling the clamping elements, which cam discs are arranged coaxial to the deflecting wheels, on which cam discs spring-loaded rollers are disposed which swivel with the clamping elements. The clamping elements in the area of the deflecting wheels can therefore be easily controlled, namely there where it is necessary that the grippers be opened. Separate drives for the controlling structure can thus be omitted.
To bridge the opening phase of the clamping elements, clamping rollers which guide the blanks can be provided in the area of the deflecting wheels. Thus the respective blank is at no time left unattended and unclamped, not even at the deflecting wheels.
For the purpose of certain preferred embodiments of the present invention it is provided that the rollers, which are disposed on the cam discs, are supported outside of the area of the cam discs on rails extending parallel to the transport belts. This prevents the blanks becoming deformed during transport due to excessively long traveling paths of the clamping elements.